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A Modeling-Based Method for Log Data Depth Matching and Calibration

IP.com Disclosure Number: IPCOM000126961D
Publication Date: 2005-Aug-15
Document File: 4 page(s) / 547K

Publishing Venue

The IP.com Prior Art Database

Related People

Michael A. Frenkel: INVENTOR [+2]

Abstract

We perform depth matching and calibration of multiple logs of the same physical nature (e.g., resistivity, etc.) measured during LWD and/or wireline measurements in vertical, deviated, and horizontal wells. To perform depth matching efficiently and in an automatic mode, we run the following inversion/modeling-based algorithm: 1. Select a depth reference log (logs). 2. Generate a reference formation model by means of reference log(s) inversion or any other correction for borehole, invasion, and shoulder-bed effects or simply squaring. These interpretations can be done for the whole logging interval or for a sequence of window-by-window well sections. Window sizes are determined based on a size of a logging instrument investigation area along the borehole and physical properties of the formation. 3. Generate synthetic log for each raw log using a reference formation model from 2. 4. Determine amount of depth shift by maximizing correlation function between raw log and corresponding synthetic log within a selected correlation window. 5. Output depth corrected logs. To perform log calibration in an automatic mode, we run the following inversion/modeling-based algorithm: 1. Select a reference log (logs). 2. Generate a reference formation model by means of reference log(s) inversion or any other correction for borehole, invasion, and shoulder-bed effects. These interpretations can be done for the whole logging interval to supply missing logs and calibrate logs or for a selected uninvaded shaly well section to calibrate logs. 3. Generate synthetic log for each raw log using a reference formation model from 2. 4. Determine calibration factors by dividing each raw log over a corresponding synthetic log. 5. Output calibrated logs. Synthetic logs can also be used to restore missing or damaged logs. The method is applicable to any LWD and/or Wireline logs, including old, conventional, and new array-type logs.

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